The Dead Media Notebook (27 page)

The Baird company was licensed to provide intermittent broadcasts from the BBC transmitters, and at least 3,000 enthusiasts “looked in” to see as well as hear some of Britain’s most popular singers and comedians.

Mechanical TV: How it works

The scanning and reproducing discs are similar. Both are mounted on driving motors, and each is punched with a spiral of small holes along the outer edge. The number of holes matches the number of lines of picture definition. At the transmitter in this mechanical system, the studio is in total darkness. A light emanates from a lamp behind the disc and, projected through the holes set in the spiral on the outer edge, scans the features of the subject’s face. The photocell converts these variations in the reflected light into the electric impulses, which, once amplified, can be transmitted by radio waves. At the receiver, the signal is converted into a sequence of bright flashes by the neon tube. The reproducing disc rotates rapidly in front of this tube, and converts each flash of the lamp into a small element of the image. The rapid speed of the disc makes “persistence of vision” possible for the looker-in.

“Persistence of vision” means that the brain retains an image for one tenth of a second after it is perceived by the eye. The rapid repetition of moving images (in film or television) tricks the brain into perceiving continuous images.

The General Electric Octagon, 1928 (U.S.A.) with RCA radio 1928 (U.S.A.) This mechanical television receiver was built for a 48- line television system developed during 1927 by Ernst W. Alexanderson, who was the Chief Consulting Engineer at the GE laboratories in Schenectady, New York. An elaborate experimental transmission on this type of receiver was internationally recognized as the first television drama. Entitled “The Queen’s Messenger”, the play had two characters, with only the heads or the hands of the four actors visible at any one time. Two actors spoke the lines, while the other two acted as “hand models”. The transmitted signal was received on a console radio and monitored through the 3” lens on the Octagon by the director, and the actors were only a few feet away. GE considered mass-production of the Octagons, but this never materialized.

Daven Tri-Standard Scanning Disc, 1928 (U.S.A.) The lack of a common standard of picture definition contributed to the demise of the mechanical television boom of the late 1920’s and early 1930’s. One solution was to make a television set that could receive a number of different standards. This Daven unit was based on a large 24” disc capable of scanning three different standards of picture definition, 24-line, 36-line and 48-line, enabling the viewer to receive more stations. The television signal was received by a short-wave radio. The operator then had to adjust the height of the neon lamp to match the correct spiral of holes, and synchronize the rotation of the scanning disc to the corresponding rotations per minute. The tiny picture would be visible in one of the three frames (marked within the black outline).

Homebrew W1IM Scanning Disc, 1928 (U.S.A.) This home-made scanning disc television unit was built by the Connecticut radio experimenter, Clifford Fraser, using hand-written instructions sent to him by the mechanical television pioneer and broadcaster, Charles Jenkins. Jenkins was aware that “Radiovision” was in its infancy and actively encouraged involvement, experimentation and the exchange of information within the amateur radio community. In the late 1920’s, he even went so far as to offer Radiovisor Kits similar to this one at $7.50 U.S. postage paid - a price so low that it meant a loss for his company.

Jenkins Model 202 Radiovisor, 1929 (U.S.A.) This mechanical scanning-drum unit was engineered, designed and manufactured by the Jenkins Television Corporation, a company founded in 1928 by the American television pioneer, Charles Francis Jenkins. As early as 1894, he presented an article in the periodical, Electrical Engineer, on a method of electrically transmitting pictures. He was one of the earliest to succeed at television transmission, and claimed to have executed the first reported transmission of television by radio in 1923. Hugo Gernsback of Radio News and Watson Davis of Popular Radio witnessed a demonstration in the same year. In 1928 Jenkins announced the birth of a new entertainment industry, “Radio Movies”. Shortly thereafter, Jenkins Laboratories Incorporated initiated 48-line silhouette broadcasting through regularly scheduled telecasts over station W3XK and a few other stations that showed “Radio Movies”. Jenkins preferred the term “Radiovision” to “Television”, which explains this unit’s name.

Baird Televisor, 1930 (U.S.A.) The Plessey model was the most popular version of the mechanical “Televisor” to be available to the British and West European retail buying public. It was engineered and designed by John Logie Baird and manufactured by the Plessey company in England. It was purchased by television enthusiasts to watch the periodic Baird Studios/BBC broadcasts available from 1929 to 1932. The 30 line images did not take up the entire “screen,” but were in fact 6cm high and 2cm wide. Instead of black and white, they were black and red due to the colour of the neon gas in the lamp. About 1,000 of these sets were originally produced and priced at just over 18 British pounds each. There were kit receivers without the tin cabinet, available from Baird’s for only 7 pounds. Baird was one of the true pioneers of television. He successfully demonstrated the possibilities of the Nipkow system of mechanical television by achieving the first television picture in October, 1925.

Western Television Corporation Visionette, 1932 (U.S.A.) Western Television Corporation played a significant role in the evolution of television in North America. Canada’s first experimental television station, which was operated by the Montreal newspaper La Presse and radio station CKAC, was supplied with Western Television equipment. The Canadian public witnessed Western Television’s technology through a special mechanical projection apparatus, which was demonstrated at Eaton’s and department stores in Toronto, Montreal and Winnipeg during 1933. In the U.S., Western’s travelling demonstrations included a 9-day run at Macy’s in New York that was witnessed by over 200,000 people. The Western Television Corporation drew on the talents of television pioneer Ulysses A. Sanabria, who is known for his use of interlaced scanning. Interlacing improved picture quality by reducing flicker. This television utilizes an interlaced aluminum scanning wheel and 3” magnifying lens. It was among the last and most advanced mechanical home televisions to be in use before the electronic sets began to show greater promise.

Source: These are excerpts from the catalog from the exhibition at the Royal Ontario Museum, Watching TV. The exhibition runs through September 15, 1996.

From Trevor Blake

The discovery leading to the possibility of mechanical television was an accident. While laying the first trans- Atlantic cable, a worker noticed that some of his tools were glowing. An analysis of the metal revealed a concentration of selenium, the metal used soon after in the earliest photoelectric cells. Selford Bidwell used a photoelectric cell to transmit an image electronically in 1881: over the course of several minutes, a two-inch square image could be sent via telegraph lines.

Three years later, Paul Nipkow was granted a German patent for the Nipkow disk a complete and functional television system in 1884.

The development of the neon tube in 1910 furthered mechanical television. Film achieves the illusion of motion by taking advantage of the persistence of vision: still images in a fixed location which are refreshed at a rate of sixteen times per second (or more) are interpreted by the human mind as moving images. Television achieves the illusion of motion in a similar but unique fashion. Rather than refresh the entire image at once, as film does with each cell that passes in front of the projector’s light, television refreshes an image one line at a time in a scanning process.

Within the cathode ray tube, an electron gun scans a single line of an image from one side to the other, then scans the line underneath it, until it has scanned an entire image.

The Nipkow disk is an earlier, mechanical means of achieving the same side-to-side, top-to-bottom scan process. It consists of a disk that rotates on its axis. A series of evenly spaced, uniformly sized holes are cut into the disk, spiraling in toward the center. The disk is housed in a box with a small viewing window: the outermost hole of the disk will form the outermost scan line visible in the viewing window, and each additional hole will form additional scan lines. The rotation of the disk as seen through the viewing window provides scanning from side to side, and the spiral placement of the holes provides scanning from outermost to innermost scan line. A light source which can be varied in intensity is placed on the opposite side of the disk behind the viewing window. As the light flickers and the disk rotates, television is achieved.

Mechanical television cameras and receivers alike use the Nipkow disk, but where the receiver uses a flickering light to produce an image, the camera uses a photosensitive cell to generate an image. The rotation of the disks is synchronized by part of the transmission signal (which has included radio, short wave and telephone) or direct wiring.

The disks rotate at around 900 rpm and initially produced television two inches square. The earliest mechanical televisions offered between 16 and 24 lines of resolution. By the late 1920s, they offered between 48 and 60 lines. Double and triple spirals of scanning holes were used, as well as scanning drums and belts. Lenses were fixed in the scan holes to project the image onto a larger screen (up to 8 inches in some cases).

Mechanical television cameras were synchronized with film projectors, allowing the transmission of film. Studio B of the BBC used a hybrid of this system: the subject was filmed, the film was instantly processed and then scanned for transmission. There was a delay of around one minute between event and transmission as the film developed.

The light required for mechanical television is intense, so much so it was nearly impossible to perform while being televised. The flying spot camera was one solution to this problem: an additional scanning disk, synchronized to the camera, cast a brilliant light on the subject in the same spot they were being scanned.

The rest of the studio, including the control room, was kept in complete darkness. Another solution to this problem was the use of multiple arrays of concave lenses to focus light into the camera more efficiently.

Source: BOOKSManly, Harold: DRAKE’S RADIO ENCYCLOPEDIA (Drank & Co. 1927) Ghirardi, Alfred: RADIO PHYSICS COURSE (Radio & Technical Pub. 1933) Zworkin, Y. K. and Morton, G. A.: TELEVISION (John Wiley 1940) Goldstein, Norm: THE HISTORY OF TELEVISON (Portland House 1991) Kisseloff, Jeff: THE BOX (Viking 1995) Ritchie, Michael: PLEASE STAND BY (Overlook Press 1994) Winship, Michael: TELEVISION (Random House 1988) Yanczer, Peter: THE MECHANICS OF TELEVISON (Peter Yanczer 1987) (Peter Yanczer, 835 Bricken Pl., St. Louis MO 63122 USA) MAGAZINES Popular Science, March 1932 Mechanics and Handicraft, Vol. 1 #1, Winter 1933 Television: Journal of the Royal Television Society, April 1995 VIDEO The Race for Television, BBC

From Trevor Blake

JOHN LOGIE BAIRD

Scotsman John Logie Baird had long been an entrepreneur and inventor. When he was twelve he built his own telephone. He had invested in chutney in the West Indies, artificial diamonds in Glasgow and soap in London. In 1918 he held the patent for the Baird Undersock, a sock worn beneath regular socks.

In 1920, at the age of 31, he began his life’s work, the undercredited discovery and development of television. Beginning with a personal ad in the London Times (“SEEING BY WIRELESS: Inventor of apparatus wishes to hear from someone who will assist [not financially] in making working model”), Baird set out to build a working television system using borrowed money and the material he had at hand, which included darning needles, hat boxes, a Rich Mix biscuit tin, sealing wax and a bicycle lantern. His Nipkow disk was cut from an old tea chest. In February 1923 he entered the shop of Hasting radio dealer Victor Mill and asked for assistance, saying “I’ve fitted up an apparatus for transmitting pictures and I can’t get it to go.”

Mills accompanied Baird back to his laboratory / apartment and waved his hand in front of the neon: when Baird shouted “it’s here, it’s here!”, the first real-time electronic moving picture in world history occurred. Not long after Baird demonstrated his system to the local press, but was evicted from his apartment. Baird relocated to London and set up a second and lab in Soho. Using ventriloquist dummies (better able to withstand the intense heat and light of his equipment), he succeeded in transmitting a televised image one yard across his room.

In March 1925 he gave the first public demonstration of television, sponsored by Selfridge’s Department store. A demonstration of television in January 1926 in Baird’s small, drafty attic apartment failed to impress the Royal Institute, particularly when the long white beard of one of the men became entangled in the mechanism.

In Autumn of the next year he transmitted eight miles, and formed a company: Television Ltd. The first recorded television images were made on 10” wax disks called Phonovisors, no later than September 1927 in Baird’s labs: he had been awarded a patent for this technology the year before. Phonovisor disks captured 12.5 frames of 30-line resolution television per second. Baird also patented Noctovision, the use of infrared light in television, and demonstrated color television (using a rotating filter system) in 1927.

By 1928, Baird Televisors sold for between 20 and 150 pounds (kits sold for 16 guineas). Baird’s assistant Benjamin Clapp travelled to New York City to receive the first transoceanic television signal. The box of equipment he used was labeled ‘experimental radio equipment’ to prevent customs from seizing it as a dangerous or profitable new technology. It took two months before a break in the weather allowed Clapp to see the image of Stukey Bill [a.k.a.“Stooky Bill”], the ventriloquist dummy head used in the Baird studio, but once the press was called in the event received one inch headlines across the nation. On the way home aboard the Berengeria, Clapp allowed the ship’s wireless operator to see his fiance in England via television while 1,000 miles out at sea.